From: Robert Dober <robert.dober@...>
Date: 2007-07-25T17:33:43+09:00
Subject: Re: Static variables in Ruby.

On 7/24/07, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> Nobuyoshi Nakada wrote:
> > Hi,
> >
> > At Tue, 24 Jul 2007 17:40:57 +0900,
> > Marcin Tyman wrote in [ruby-talk:261483]:
> >> Is any way to define static variables over function? As class static
> >> variables there is possible to define a static class variable as
> >> @@name_of_var. But I'm not sure if Ruby let define such variables in
> >> functions (like in C/C++)
> >
> >   def foo(x)
> >     (0..0).instance_eval{x,@x = @x,x}
> >     x
> >   end
> >   3.times{|i|p foo(i)} #=> nil, 1, 2
> >
> > The literal object can be Float, Regexp or Bignum, but Range
> > would be faster a bit.
> >
>
> Interesting. That is because Float, Regexp, and Bignum are instantiated
> per scope, right?
>
> Sometimes a little abstraction leakage can be useful!
>
> --
>        vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407
>
>
I did not believe this,and why should I?
But it seems to be true ;)
def foo(x)
  (0..0).instance_eval{x,@x = @x,x}
  x
end

3.times{ |i| puts foo(i) }
(0..0).instance_eval{@x=42}
3.times{ |i| puts foo(i) }

Run this for a pleasant surprise :)

Robert

-- 
I always knew that one day Smalltalk would replace Java.
I just didn't know it would be called Ruby
-- Kent Beck